Question: 8 folders cost $10.48. Which equation would help determine the cost of 15 folders?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 8 folders. We want to know the cost of 15 folders. We can write the numbers of folders as a proportion: $\dfrac{8}{15}$ We know 8 folders costs $10.48. We can let $x$ represent the unknown cost of 15 folders. The proportion of these costs can be expressed as: $\dfrac{\$10.48}{x}$ The cost changes along with the number of folders purchased, and so the two proportions are equivalent. $\dfrac{8}{15} = \dfrac{\$10.48}{x}$